The present invention relates to multilayer substrates, methods for manufacturing multilayer substrates and electronic devices.
Conventional art of multilayer substrates include (1) printed circuit boards (copper-lined multilayer substrates), (2) ceramic multilayer substrates, and (3) thin film sequential lamination substrates.
A fabrication process by the method for (1) is as described below. First, as shown in FIG. 2(a), a wiring 2 is printed on a film 100 of a substrate to form a wiring substrate. Next, as shown in FIG. 2(b), a plurality of wiring substrates are simultaneously stacked and bonded together with a copper film 103 and a through hole 104 is formed in the multilayer substrate as shown in FIG. 2(c) by drilling the multilayer substrate with a drill. Finally, as shown in FIG. 2 (d), the through hole 104 is plated to permit electrical connection through a plating film 105. This state of art is described in Micro Electronics Packaging Handbook (Rao R. Tummala and J. Rymazewski, p 684, Nikkei BP Co., Ltd. (March 1991)).
A fabrication process by the method for (2) is as described below. First, as shown in FIG. 3(a), a hole 107 is formed in a sheet 101 obtained by molding a ceramic raw material called "green sheet" by using a punch and a via hole layer is formed as shown in FIG. 3 (b) by forming a via hole 106 by plating. In addition, a wiring pattern 2 is printed at the specified position on the via hole layer as shown in FIG. 3(c). Finally, a plurality of via hole layers having the wiring pattern which is thus formed as described above are registered, stacked and sintered as shown in FIG. 3(d). This state of art is described in Micro Electronics Packaging Handbook (Rao R. Tummala and J. Rymazewski, p 382, Nikkei BP Co., Ltd. (March 1991)).
A fabrication process by the method for (3) is as described below. First, as shown in FIG. 4(a), a resin 109 is applied onto a ceramic multilayer substrate 102 and a first thin film wiring substrate having a wiring 110 is formed on a layer of this resin 109 through thin film wiring substrate processes such as for forming a resist, a resist for exposure, cleaning and plating, a through hole, and a wiring pattern. In addition, a multilayer substrate having a multilayer thin film wiring can be fabricated on the ceramic multilayer substrate 102 by laminating a plurality of wiring substrates on the first thin film wiring substrate by repeating the above-described thin film wiring substrate forming processes. This state of art is described in Micro Electronics Packaging Handbook (Rao R. Tummala and J. Rymazewski, p 554 and p562, Nikkei BP Co., Ltd. (March 1991)).